1. Field of the Invention
The present invention relates to an optical reading/writing apparatus and method.
2. Description of the Related Art
In recent years, a high-density optical storage medium such as a Blue-Ray disk (BD) that can store a large capacity of high definition video data and high quality audio data has been developed.
As standardization of the BD is quickly progressed, it is expected that related products will be developed and commercialized.
As a next generation of the optical reading/writing driver, a variety of drives relating to the BD have been introduced. The BD can store 25 GB data on its single surface. When the BD is a dual layer disk, it can store about 50 GB video/audio data.
In order to increase the storage capacity of the optical storage medium, a wavelength of laser beams is shortened or a numerical aperture of an object lens is enlarged.
FIG. 1 is a schematic view of an optical reading/writing apparatus according to the related art.
Referring to FIG. 1, beams emitted from a laser diode 10 are converted into parallel beams by a collimator lens 11. Then, the parallel beams are converged on a disk by an optical lens 13 after they pass through a beam splitter 12.
The beam reflected from the disk 14 is transmitted to the beam splitter 12 via the object lens 13 and is then reflected to an optical detector 16 via a sensor lens 15.
However, in an optical system depicted in FIG. 1, the reduction of the wavelength to increase a storage capacity is at the end of its limitation. In addition, the enlargement of the numerical aperture in a conventional far-field optical reading/writing method cannot sufficiently increase the storage capacity.
Therefore, in order to increase the storage capacity, a near-field optical reading/writing method using a solid immersion lens (SIL) has been used. This is illustrated in FIG. 2.
As shown in FIG. 2, in the near-field method, an SIL 22 is disposed below an object lens 21. The SIL 22 is semi-spherical and formed of a medium having a refractive index greater than 1. By the SIL lens 22, the numerical aperture of the object lens 21 becomes n*NA to be above 1, thereby dramatically increasing the storage capacity.
Meanwhile, as shown in FIG. 3, since the SIL 22 is fixedly mounted on a barrel 30 together with the object lens 21, it is impossible to use other types of disks. That is, a variety of disks such as the BD, the digital versatile disk (DVD), a compact disk (CD) and the like cannot be compatibly used. Therefore, users have to use both existing optical drives and new optical drives to use both new and existing optical disks.